It is known to provide chairs with backrests, especially when such chairs are for use in offices or other environments where prolonged sitting is likely. Such chairs generally take the form of an inner shell with suitable padding or upholstery fitted over the shell, such as shown in Kaneda U.S. Pat. No. 5,102,196. The resulting seat portion of such chairs is generally supported on a pedestal or similar support structure.
Although such chairs are generally comfortable, they have various drawbacks and disadvantages. For example, the support structures for these ergonomically designed chairs make them difficult if not impossible to stack on each other in a telescoping and space-saving configuration, either because of the design of the support structures themselves or their inherent weight.
Furthermore, the inability to stack such chairs means that they are cumbersome and difficult to store. The storage disadvantage becomes magnified when there are multiple chairs involved, such as may be found around a table, in a conference room, or in any environment where the seating of multiple persons is the norm.
Another disadvantage to the ergonomic chairs of the current art is that they tend to be mechanically and structurally complex. As such, the chairs may be difficult or non-intuitive to operate, or otherwise require an "owners manual" to be effectively used. The structural complexity also makes such chairs expensive to manufacture and purchase.
Although chairs of the current art have adjustable settings for the backrest, seat height, tilt, etc., the chairs are generally adjusted for the size, weight, and habits of one particular user at time. As such, the interchangability of such ergonomic chairs is inherently limited: another user must content him- or herself with the settings of the previous user, which may not be ergonomically optimal; or such other user must go through the sometimes painstaking process of readjusting the chair to obtain make it comfortable or ergonomic.
As a further disadvantage, the adjustments to an ergonomic chair which are optimal for certain seated activities may be sub-optimal or otherwise inappropriate for other activities. In other words, ergonomic chairs of the current art often treat the seated individual as relatively static over time, merely occupying three-dimensional space. Such an approach ignores that the seated user is occupying the three dimensional space over a period of time, during which the user is engaged in a variety of activities, each with its own ergonomic demands or requirements. Chairs of the current art are frequently unable to adapt to the different ergonomic requirements of such different activities taking place over time in the chair.
When an ergonomic chair is inappropriately adjusted either for the user or for the user's activity, this often means that a complex and expensive piece of equipment is not being appropriately used. Such a poorly adjusted chair will result in pressure being exerted on the seated user at inappropriate locations. Such pressure makes the user uncomfortable at a minimum, and is likely to fatigue or otherwise debilitate the person seated in the maladjusted chair over time.
Attempts at solving the foregoing drawbacks and disadvantages have generated their own shortcomings. For example, on the other end of the spectrum from the structurally complex, non-stacking chair, is the basic, L-shaped, stackable chair with an open tubular or wire frame support. The legs of the frame are flared or otherwise structured so that the basic L-shaped chairs can be stacked one atop the other in a telescoping fashion to save storage space.
In order for such chairs to be stacked on each other, however, the design generally sacrifices most, if not all, of its ergonomic features. For example, the seat portions of such chairs must generally remain in an L-shape in order to be stacked, and such L-shape does not conform well to the curves of the user's back, particularly the lumbar or lower back region thereof.
Prior art attempts to maintain in a single chair design both the convenience of stacking as well as ergonomic features have had mixed results. U.S. Pat. No. 4,418,9582 to Watkin is an example of such prior attempts. Although chair shell disclosed in the Watkin patent is formed of a resilient material such as polypropylene, it does not provide sufficient ergonomic support to the user. For example, it is desirable to maintain a certain amount of independent motion between the areas of the chair seat which are supporting the bottom, lower back, and upper back, respectively, of the seated user, and the one-piece shell of Watkin does not provide a sufficient amount of such independent motion in a manner consistent with ergonomic principles.
Accordingly, there is a need for a chair with improved back support, particularly in the so-called lumbar or lower-back region, and with improved ergonomic features of the chair seat. There is a need for such a chair also to be capable of being stacked with one or more identical chairs of the same general configuration.
There is a further need for such a chair to respond to the changing ergonomic needs of the user over time.
There is a still further need for such a chair to have substantially independent points of support for the users bottom, lower back, and upper back, respectively.
There is a yet a further need for such chair to be self-adjusting as between different users.